You can take higher-resolution screenshots with the zoom option. This isn't exactly the same as taking a screenshot with a HiDPI ("Retina") device: it is like increasing the zoom to 200% in a desktop browser and doubling the height and width of the browser window. This differs from using a HiDPI device because some web pages load different, higher-resolution images when they know they will be displayed on a HiDPI device (but using zoom will not report that there is a HiDPI device).

Vectorization

All parameters of function webshot. That means that multiple screenshots can be taken with a single command. When taking a lot of screenshots, vectorization can divide by 5 the execution time.

# Take a screenshot of different sites
webshot(c("https://www.r-project.org/", "https://github.com/wch/webshot"),
file = c("r.png", "webshot.png"))
# Save screenshots of the same site in different formats
webshot("https://www.r-project.org/", file = c("r.png", "r.pdf"))
# Take screenshots of different sections of the same site.
# Note that unlike arguments "url" and "file", a list is required to specify
# multiple selectors. This is also the case for arguments "cliprect" and
# "expand"
webshot("http://rstudio.github.io/leaflet/",
file = c("leaflet_features.png", "leaflet_install.png"),
selector = list("#features", "#installation"))

Screenshots of Shiny applications

The appshot() function will run a Shiny app locally in a separate R process, and take a screenshot of it. After taking the screenshot, it will kill the R process that is running the Shiny app.

# Get the directory of one of the Shiny examples
appdir <- system.file("examples", "01_hello", package="shiny")
appshot(appdir, "01_hello.png")

Manipulating images

If you have GraphicsMagick (recommended) or ImageMagick installed, you can pass the result to resize() to resize the image after taking the screenshot. This can take any valid ImageMagick geometry specifictaion, like "75%", or "400x" (for an image 400 pixels wide). However, you may get different (and often better) results by using the zoom option: the fonts and graphical elements will render more sharply. However, compared to simply resizing, zooming out may result in slightly different positioning of text and layout elements.

You can also call shrink(), which runs OptiPNG to shrink the PNG file losslessly.